I am wondering where is the problem:
a) when playing the video under mplayer with Beryl & Nvidia drivers 9625 the video is choppy
b) glxgears drops from 12000 to 3400 - but when I will double click the window bar - so the
window become shadeless - and thus it's drawing only on offscreen pix buffer the result
is back to 12000 !!!

this - and especially the b) leads to conclusion that the slowest part is compositing one.
But where is the fault - inside Beryl or Nvidia drivers ?